Motor vehicle batteries frequently power a variety of auxiliary devices, such as, for example, two-way radios, AM/FM radios, TV's, DVD players, cellular phones, radar devices, GPS devices, data terminals, and computers. Many of these devices are memory intensive and/or consume a lot of power. These devices often remain powered on when the vehicle is unattended without regard to drain on the vehicle's battery. While such devices may be left in a powered on state to perform various functions (e.g., downloading data), the most common reason the devices remain powered on is the inconvenience of manually turning them off each time an operator stops or leaves the vehicle. As a result, undesired wear, drain, or unintentional discharge of the battery may occur.